Dewaxing with solvent



Patented Sept. 21, 1943 f i 1; 3

r I DEWAXING WITH SOLVENT I v Luke B. Goodson, Phillips, Tex, James V. Mont Okmulgee, and Robert W. Henry, ,1 I Bartlesville, kla., assignors to Phillips Petroj leum Company, a corporation of Delaware No Drawing. Application oetoberas, 1940,

I Serial No. 363,209 I:

-3 Claims. (o1. mam

. This invention relatesto the dewaxing of mineral oils and more particularly it relates to improved de'waxing, solvents therefor. 1

The useof low boiling aliphatic acetates as solvents or as components in solvent mixtures is known. Those low boiling acetates comprise aliphatic acetates'containing 3 to 6 carbon atoms permolecule, for example, methyl acetate, ethyl acetate, propyl, acetate, butylacetate, etc.

An object of this invention is to furnish an improved solvent for the dewaxing of mineral oils.

Another object of this invention is to furnish an improved solvent which may be used alone or in conjunction with wax antisolvents for the dewaxing of mineral oils.

Still another object of this invention is to furnish a dewaxing solvent which possesses sufficient solubility for the; mineral oil at dewaxing temperatures that solubility nhancers need not be used.

Still other objects andv advantages will be apparent to those skilled in the art from a-studyof. the following disclosure.

We have found that .the aliphatic acetates, containing 7 to 12 carbon atoms per molecule including such acetates as amyl acetate, hexyl acetate, heptyl acetate, octyl acetate, decyl acetates,and the respective iso compounds, etc., possess unusual properties 'which make them excellent solvents for use insolvent dewaxing of mineral oils, etc. For example, amyl acetate exhibits a selective action for oil over wax in that at low temperatures it has a much higher solubility for the oil component than for the wax component, thus making it possible to dewax oils'of both high and low viscosity index under widely differing conditions. Furthermore, the, wax crystals obtained from a solution of waxy oil in this solvent are large and sharply defined and are thus conducive to high filter rates'which are very desirable from an economic standpoint. The comparatively small difierential between the devvaxing temperature and the pour point of the dewaxed oil results in decreased refrigeration costs. As an additional advantage, the low miscibility temperature of these acetates, and especially amyl acetate with mineral oils makes it possible to add a wax antisolvent, such as acetone, and decrease the dewaxing differential still further. While the aliphatic acetates containing 7 to 12 carbon atoms per molecule mentioned above function exceptionally well as dewaxing solvents, we prefer to use amyl acetate because of its commercial availability.

When the aforementioned amyl acetate is used with known wax antisolvents such asta'cetone,

methyl ethyl ketone, 'dipropyl ketone, 'dibutyl ketone, and other aliphaticketones, pyridine, picolines, furfural, aniline, nitrobenzene, etc, exceptionally good results are obtained. The aliphatic acetates, containing '7 to l2;carbon atoms per molecule, and especially amyl acetate,- are sufiiciently good solvents foroil at dewaxing temperaturesthat solubility enhancergneed not be used. Similarly, these acetates possess verylow melting points, for example, amyl acetatemelts at about -F., and-theaddition of another component toprevent crystallization of the solvent at dewaxing. temperatures is unnecessary. These points-are decided advantages since. it is much easierto control solvent 'ratiosin a two component solventthan in a three. component solvent. Y o 1 The following examples .serve to illustrate our invention; I

One vvolumeof treated waxy Mid-Continent lubricating oil stock of 70 seconds Saybolt universal viscosity at 210 F. and viscosity indexwas mixed with three volumes of amyl acetate and the mixtureheated to .150? F. to insure rapid and complete solution. The mixture wasthenshock chilled to 0 F.,to precipitate the wax and; the

latter. was filtered out in the conventional man:- I The solvent was removed from the oil by distillation and gas stripping leaving an oil which had a pour pointof 20 F. v 1;

"Example II One volume of treated waxy Mid-Continent lubricating oil stock of 70-seconds Saybolt universal viscosity at 210.? F. and 85 viscosity index was mixedwith four volumes of a'solvent composed of 30% acetone, 50% benzol and 20% toluol, chilled to 0 F. and filtered in' the conventional manner. tion and gas stripping leaving an oil of 15 F. pour point.

Example III was heated to insure complete solution, then shock chilled to 0 F. to precipitate the wax.

The wax was filtered from the chilled solution in the conventional manner and the solvent re- The solvent was removed by distilla moved from the oil by distillation and gas stripping leaving an oil of F. pour point.

From the above described examples it is evident that the solvent composed of amyl acetate and acetone is superior to the one composed of benzol, acetone and toluol in the relative proportions as given in Example II, whichlattei' solvent mixture is the well known benzol-acetorie dewaxing solvent.

In carrying out our invention, we do not wish to be limited by any special type of dewaxing apparatus, since essentially standard dewaxing equipment is satisfactory. For dewaxirig of the above-mentioned Mid-Continent lubricating oil stock at 0 F., for example, one volume of the oil to be dewaxed is mixed with three volumes of amyl acetate solvent or with three volumes of solvent mixture composed of approximately 70% amyl acetate and 30% acetone, depending upon the desired pour point of the clewaxed oil, the mixing being carried out in essentially any type of mixer at slightly elevated temperature, say from 120 to 140 F., to-insure complete and rapid solution. The warmed oil-solvent solution is shock chilled to 0 F.,'as in Carbondale chillers, and filtered in conventional filters. The filtration is rapid-"since the wax crystals formed in our solvent are distinct and sharp-edged. The slack wax may be washed with additional solvent at the dewaxing temperature to remove adher irig'oil-solvent solution, and the combinedfiltrate solution and washings comprising dewaxed oil and solvent mixture are conducted'to a solventoil separating apparatus. This separating apparatus may comprise a conventional pipe heater and fractionating tower from which the solvent mixture is removed overhead as vapors and the oil passes from the lower portion thereof 'and is conducted to storage. The solventvaporsIfrom the abovementioned fractionator are condensed and conducted to intermediate storage preparatory to reuse.

We have found it possible to use these aliphatic acetates under a wide range of operating con-- ditions. By operating conditions such variables as solvent to oilratio, solvent to wax antisolvent ratio, cooling rate, blending temperature, etc., are included. To one skilled in the art, it-will be apparent that our solvents may be 'use'din a wide range of solvent to oil ratios, as well as difi'erent concentrations of the components com prising the solvent, depending upon the nature of the oil to be dewaxed and on the method of separating the wax from the solution. The use of a 3 to l solvent to oil ratio and a 3 to 1 solvent mixture (solvent and wax anti-solvent) to foil ratio gave good results regarding pour point of the finished oil and filter rates of the chilled oilsolvent-wax mixture. The boiling points of the above mentioned acetates are suificiently low to permit complete separation of solvent from oil.

By using our solvent compounds or materials as described above we obtain substantially waxfree oils having pour points from 5 to 20 F. above the dewaxing temperatures, and in every case these pour points are well within the range of effectiveness of commercial pburpoint depressors. Individual acetates, as for example, amyl acetate, hexyl acetate, etc., as chemically pure materials may be used in our process. We have found that the commercial or technical 'g'rade'of acetates gives excellent results in dewaxin'g operations. This commercial or technical grade of product usually contains small proportions of extraneous material, for example, 'conimercial'amyl acetate may contain a small proportion of other acetates, as well as very smallamounts of such materials as alcohols or ethers. The presence of other acetates is not objectionable to the successful operation oi our process since individual acetates 'or: mixtures of acetates work. equally well. i The presence of small quantities of such materials as alcohols,

V ethers, etc., 'as impurities,- has failed to impede the utility of our acetate dewaxing solvents.

To those skilled in the alt-many applications and ;uses ofthe above solvents will be apparent without departing-from-the spirit and scope of our invention. For this reason, We do not wish to be limited, in any manner by the examples given, but only by the following claims.

We claim: l i

1. The process ofdewaxing mineral olls including the steps of mixing the waxy 'oil with a dewaxing solvent comprising amyl acetate and a wax antisolvent in which the antisolven'tgis acetone, chilling the mixture of "oil andsolvent to precipitate the wax, ahdremoving the precipi= tated wax. I

2. The process of 'dewaxii'ig mineral oils including the steps of mixing the waxy 'oil with a dewaxing solvent comprising sevent per cent by volume of amyl acetate and thirty 'perbent by volume of acetone, chilling the mixture to precipitate the wax and separating the precipi tated wax;

3. The process of dewaxing 'mineral oils including the steps of mixing the waxy oil with a. dewaxing solvent comprisingan' aliphatic acetate selected from'a group of aliphatic acetates con: tained within the range of? to 12 carbon atom molecules and acetone as a wax" ahtisoive'm, rapidly chilling the mixture tofprecipita'te the wax and removing the thus precipitated was.

LUKEB. GOOD'SQN." H JAMES Y. MONTGOMERY. ROBERT HENRY. 

